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SIPS: DESIGN FLEXIBILITY Structural insu- 1. A SIPs house is a high-performance building with very low air leakage and high thermal efficiency. Roof and wall panels, insulated with foam, are assembled just like a panelized house. Doors and windows will be added once the shell is complete. lated panels can be used for just about any architectural style and finished with a variety of materials. Like panelized houses, a SIPs house goes up in a matter of days, reducing on-site exposure to the weather. 2. One recently built demonstration house in Tennessee costs only 85¢ a day to heat and cool and is 70% tighter than what the government's model energy code recommends. industry is selling. As important are the advantages of a tight building envelope and low energy consumption. Bill Wachtler, the executive director of the Structural Insulated Panels Association, says that SIPs houses are 50% more energy efficient than conventional stick-framed buildings. One recently built demonstration house in Tennessee, he says, costs only 85¢ a day to heat and cool and is 70% tighter than what the government's model energy code recommends. Wall panels are typically 4:1 in. or 6:1 in. thick, filled with either expanded-polystyrene (R-4 per in.) or polyisocyanurate (R-7 per in.) foam. Roof panels may be up to 12 in. thick. In addition about $2,000 higher, but reduced job-site labor would make up the difference. Bill Chaleff, a Long Island, N.Y., architect the panels also are effective air barriers. Panels come with door and window openings already cut. Manufacturers use several methods of joining panels on site. to offering high insulation values, Panels are manufactured and sold by a number of companies, all of which may offer slightly different panel sizes and design services. But companies typically are able to work with plans submitted by a builder or homeowner and translate a stick-built design into a SIPs design. "You can build anything with SIPs," Wachtler says. Not the cheapest option One thing the industry doesn't push is low cost. "Compared to what?" Wachtler asks. "If you want very high energy efficiency, SIPs is very competitive. Ifit's cheap construction, it isn't. The fairest way is to look at performance." He says he took plans for one 3200sq.-ft. house and compared costs of stick-building to using SIPs. He found that material costs for the SIPs structure were 62 FINE HOMEBUILDING who works exclusively with structural insulated panels, says it's cheaper to build a highperformance house with SIPs than it is with conventional framing. In addition, he says the buildings are two or three times stiffer, making it easier to meet wind-load building requirements in some parts of the country. Duncker is another fan. His own house is made from structural insulated panels (FHB #147, pp. 106-1 1 1). He originally had considered the panels for the roof alone, but the panel maker in his area suggested a bid for the whole house. Because the panels are so stiff, Duncker found that he could skip the seismic reinforcements that otherwise would be required and that the SIPs shell is highly energy efficient. "When we added all those things together, they came out to be just about the same as the cost of framing, insulating, and structural hold-downs," he says. "We were kind of pushing the building season at that point, so we thought we'd give it a shot." Bugs and roof sag There's no telling where the stories started, but panel manufacturers seem used to fielding questions on whether the foam cores of the panels harbor carpenter ants and termites. Michael Morley, a Kansas contractor and insulated-panel dealer, says that such fears are unfounded. Some panel manufacturers treat the foam core and strand-board skins with borate to deter infestations, and Morley says SIPs buildings are no more susceptible to insect damage than any other wood building. Photos this page: Courtesy of the Structural nsulated Panel Association I